Color management: add OCIO aware utility functions for transform to/from XYZ.

4 files changed, 51 insertions, 4 deletions

diff --git a/source/blender/imbuf/IMB_colormanagement.h b/source/blender/imbuf/IMB_colormanagement.h
index 29e54158f4b..437a699208b 100644
--- a/source/blender/imbuf/IMB_colormanagement.h
+++ b/source/blender/imbuf/IMB_colormanagement.h
@@ -71,6 +71,8 @@ const char *IMB_colormanagement_get_rect_colorspace(struct ImBuf *ibuf);
 
 BLI_INLINE float IMB_colormanagement_get_luminance(const float rgb[3]);
 BLI_INLINE unsigned char IMB_colormanagement_get_luminance_byte(const unsigned char[3]);
+BLI_INLINE void IMB_colormangement_xyz_to_rgb(float rgb[3], const float xyz[3]);
+BLI_INLINE void IMB_colormangement_rgb_to_xyz(float xyz[3], const float rgb[3]);
 
 /* ** Color space transformation functions ** */
 void IMB_colormanagement_transform(float *buffer, int width, int height, int channels,
@@ -99,6 +101,9 @@ void IMB_colormanagement_colorspace_to_scene_linear(float *buffer, int width, in
 void IMB_colormanagement_scene_linear_to_color_picking_v3(float pixel[3]);
 void IMB_colormanagement_color_picking_to_scene_linear_v3(float pixel[3]);
 
+void IMB_colormanagement_scene_linear_to_srgb_v3(float pixel[3]);
+void IMB_colormanagement_srgb_to_scene_linear_v3(float pixel[3]);
+
 void IMB_colormanagement_scene_linear_to_display_v3(float pixel[3], struct ColorManagedDisplay *display);
 void IMB_colormanagement_display_to_scene_linear_v3(float pixel[3], struct ColorManagedDisplay *display);
 
diff --git a/source/blender/imbuf/intern/IMB_colormanagement_intern.h b/source/blender/imbuf/intern/IMB_colormanagement_intern.h
index 84e0bd6c599..ee3d207a8db 100644
--- a/source/blender/imbuf/intern/IMB_colormanagement_intern.h
+++ b/source/blender/imbuf/intern/IMB_colormanagement_intern.h
@@ -42,6 +42,8 @@ struct OCIO_ConstProcessorRcPtr;
 struct ImBuf;
 
 extern float imbuf_luma_coefficients[3];
+extern float imbuf_xyz_to_rgb[3][3];
+extern float imbuf_rgb_to_xyz[3][3];
 
 #define MAX_COLORSPACE_NAME          64
 #define MAX_COLORSPACE_DESCRIPTION  512
diff --git a/source/blender/imbuf/intern/colormanagement.c b/source/blender/imbuf/intern/colormanagement.c
index f2244b6ab5c..395bb90d686 100644
--- a/source/blender/imbuf/intern/colormanagement.c
+++ b/source/blender/imbuf/intern/colormanagement.c
@@ -93,10 +93,12 @@ static int global_tot_display = 0;
 static int global_tot_view = 0;
 static int global_tot_looks = 0;
 
-/* Set to ITU-BT.709 / sRGB primaries weight. Brute force stupid, but only
- * option with no colormanagement in place.
- */
-float imbuf_luma_coefficients[3] = { 0.2126f, 0.7152f, 0.0722f };
+/* Luma coefficients and XYZ to RGB to be initialized by OCIO. */
+float imbuf_luma_coefficients[3] = {0.0f};
+float imbuf_xyz_to_rgb[3][3] = {{0.0f}};
+float imbuf_rgb_to_xyz[3][3] = {{0.0f}};
+float imbuf_xyz_to_linear_srgb[3][3] = {{0.0f}};
+float imbuf_linear_srgb_to_xyz[3][3] = {{0.0f}};
 
 /* lock used by pre-cached processors getters, so processor wouldn't
  * be created several times
@@ -563,6 +565,10 @@ static void colormanage_load_config(OCIO_ConstConfigRcPtr *config)
 
 	/* Load luminance coefficients. */
 	OCIO_configGetDefaultLumaCoefs(config, imbuf_luma_coefficients);
+	OCIO_configGetXYZtoRGB(config, imbuf_xyz_to_rgb);
+	invert_m3_m3(imbuf_rgb_to_xyz, imbuf_xyz_to_rgb);
+	copy_m3_m3(imbuf_xyz_to_linear_srgb, OCIO_XYZ_TO_LINEAR_SRGB);
+	invert_m3_m3(imbuf_linear_srgb_to_xyz, imbuf_xyz_to_linear_srgb);
 }
 
 static void colormanage_free_config(void)
@@ -1927,6 +1933,14 @@ void IMB_colormanagement_colorspace_to_scene_linear(float *buffer, int width, in
 	}
 }
 
+/* Conversion between color picking role. Typically we would expect such a
+ * requirements:
+ * - It is approximately perceptually linear, so that the HSV numbers and
+ *   the HSV cube/circle have an intuitive distribution.
+ * - It has the same gamut as the scene linear color space.
+ * - Color picking values 0..1 map to scene linear values in the 0..1 range,
+ *   so that picked albedo values are energy conserving.
+ */
 void IMB_colormanagement_scene_linear_to_color_picking_v3(float pixel[3])
 {
 	if (!global_color_picking_state.processor_to && !global_color_picking_state.failed) {
@@ -1975,6 +1989,22 @@ void IMB_colormanagement_color_picking_to_scene_linear_v3(float pixel[3])
 	}
 }
 
+/* Conversion between sRGB, for rare cases like hex color or copy/pasting
+ * between UI theme and scene linear colors. */
+void IMB_colormanagement_scene_linear_to_srgb_v3(float pixel[3])
+{
+	mul_m3_v3(imbuf_rgb_to_xyz, pixel);
+	mul_m3_v3(imbuf_xyz_to_linear_srgb, pixel);
+	linearrgb_to_srgb_v3_v3(pixel, pixel);
+}
+
+void IMB_colormanagement_srgb_to_scene_linear_v3(float pixel[3])
+{
+	srgb_to_linearrgb_v3_v3(pixel, pixel);
+	mul_m3_v3(imbuf_linear_srgb_to_xyz, pixel);
+	mul_m3_v3(imbuf_xyz_to_rgb, pixel);
+}
+
 /* convert pixel from scene linear to display space using default view
  * used by performance-critical areas such as color-related widgets where we want to reduce
  * amount of per-widget allocations
diff --git a/source/blender/imbuf/intern/colormanagement_inline.c b/source/blender/imbuf/intern/colormanagement_inline.c
index 4a55f8f86ae..37ef8779f58 100644
--- a/source/blender/imbuf/intern/colormanagement_inline.c
+++ b/source/blender/imbuf/intern/colormanagement_inline.c
@@ -62,4 +62,14 @@ unsigned char IMB_colormanagement_get_luminance_byte(const unsigned char rgb[3])
 	return unit_float_to_uchar_clamp(val);
 }
 
+void IMB_colormangement_xyz_to_rgb(float rgb[3], const float xyz[3])
+{
+	mul_v3_m3v3(rgb, imbuf_xyz_to_rgb, xyz);
+}
+
+void IMB_colormangement_rgb_to_xyz(float xyz[3], const float rgb[3])
+{
+	mul_v3_m3v3(xyz, imbuf_rgb_to_xyz, rgb);
+}
+
 #endif  /* __IMB_COLORMANAGEMENT_INLINE_H__ */